Adventures of Cullen Geiselman, Batgirl

It's maternal season, Cullen Geiselman told me. She was looking up at the Waugh bridge, and from the inch-wide crevices that stripe the bridge's underside, thousands of sleepy little bat faces were looking back down at us. Cullen said that they were all babies and nursing mothers. This time of year, the dads nest elsewhere.

Batgirl, people call Cullen. It's inevitable: Her life could belong to a comic-book alter ego. The beautiful descendant of an oil baron, she worked for Bat Conservation International, then a few years ago earned her Ph.D. from Columbia (Gotham City!) with a dissertation about South American rainforest bats. I didn't bother to ask about the cape and mask she dons when saving the world. She's heard the joke too often.

Instead, we watched bats. It was dusk, and about 50 people had gathered around the bridge, waiting for the mother bats to pour out, hundreds at a time, in search of food. Under the bridge, a night heron stalked back and forth, peering grumpily into the bayou. Sometimes babies fall off the bridge, Cullen explained. The heron was waiting to gobble them.

Of the 1,200 species of bats in the world, eight live in Houston, Cullen said. Most of those in the bridge colony are Mexican free-tailed bats, possibly mixed with a few close relatives.

The babies had been born in June. Mexican free-tailed bats have only one baby at a time, and to me it's astounding that any of them survive. As soon as they're born, they have to hang by their feet. The mother has to eat enough bugs not only to power her own high-metabolism self, but also to produce milk for her fast-growing baby.

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Wine and Cheese and Bats

What: Over wine and cheese, Cullen Geiselman will discuss Houston's eight bat species, then lead a bat walk through the arboretum.

There was a time, Cullen said, when scientists thought that in a big Mexican free-tailed colony, mothers would nurse any baby at all, whether it was her own or not. How, after all, could a mother be expected to find her infant again? The Waugh bridge colony, a relatively small group, has around a quarter-million bats. And Bracken Cave, outside San Antonio - the biggest mammal colony not just in Texas, but in the world - is home to roughly 10 million. In crowds like that, it seemed that surely a mother would nurse whatever baby was nearby.

But it doesn't work that way, Cullen explained. Scientists now know that after nights of bug-hunting, the mothers come back, morning after morning, to nurse their own. Sure, as a mom crawls through the bat-crowded bridge crevices, other babies will try to grab a snack from her. But it's her own baby that the mother seeks out. She searches for its voice, its smell. And somehow, improbably, she finds it. The mother returns.

Those Cullens

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Lifestyle

Cullen is one of those Cullens, the descendants of oilman Hugh Roy Cullen, part of the sprawling family whose name seems to attach naturally to words like "Center," "Theater" and "Foundation." Cullen's mom, Beth Robertson, followed in her own mother's footsteps, throwing herself into the family tradition of good works. Beth served on gazillions of boards of directors, working to save the world through education, conservation and medical care. Cullen didn't plan to do the same.

When Cullen was 12 or 13, Merlin Tuttle, the founder of the Austin-based Bat Conservation International, came to Houston to deliver a talk at the zoo. Beth, as a member of the Houston Zoological Society board, invited Tuttle to stay at their house. Beth became entranced by bats, traveling to see them and taking animal-crazy Cullen along.

Years later, when Beth complained about Cullen's long stay at a middle-of-nowhere research station in French Guiana, Cullen would remind her: "Mom, it was you who introduced me to bats. It's your fault."

That didn't comfort Beth. Once, visiting Cullen at Columbia, an environmentalist asked Beth to sign a petition. "Sorry," she snapped. "I've already given my daughter to the environment."

Beth was happy in the winter of 2009, when Cullen left cold New York to finish writing her dissertation in Houston. Cullen expected the Houston stay to be temporary: She planned to work in academia, to teach and do research at whatever university offered her a shot at tenure. Bats, not boards, would be her life.

But the recessionary job market was terrible. Cullen scored near miss after near miss as she looked for a post-doc job. One potential supervisor didn't get tenure; another got hit by a car. And in the meantime, the combined gravitational pull of Houston and her family grew stronger.

She still does bat research, still goes to international bat conferences. In 2009, with her adviser and another researcher, she published a book to help biologists identify seeds found in bat guano in Central and South America. She hopes to do similar research in Asia and Africa.

But - shades of Beth - Cullen now finds herself serving on seven boards of directors, accepting the full-time job that it can be, being one of those Cullens, the kind who try to save Houston and the world. Cullen is chair of the Cullen Trust for Health Care, and a board member of six other nonprofits: the Houston Zoo, the Houston Arboretum and Nature Center, the Contemporary Art Museum of Houston, the University of Houston's Blaffer Art Museum, Houston Advanced Research Center and, of course, Bat Conservation International.

These days, she shares an office with her mother. And Beth is thrilled: Somehow, improbably, her daughter has returned.